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Used Servo Motors Reborn How Does It Happen

Used Servo Motors Reborn How Does It Happen

By Jade York
If you have a line of CNC machining center(s), a process that uses robots, or a machine that uses servos as indexers for part placement, you know that servo motors are critical. In fact, they are usually one of the first part types in these machines to need service or replacement.

Servo motors repeat the same motion for long periods of time exceptionally well, but eventually, they break down. The common reasons are worn-out bearings, contamination, or overloading the motor with jammed up processes.

A new replacement from an OEM is costly and can take several weeks. If you’ve ever asked an OEM for a quote or lead-time, you probably know that all too well.

That’s where used servo motors come in. If remanufactured or refurbished to factory specs, they can be viable replacements for broken motors. They cost less, work just as well, and depending on your supplier, can also come with a warranty.

For example, at Repair Zone, we have a team of specialists that make used servo motors like new again. It varies by model and manufacturer, but cost saving can be significant with little to no lead-time.

Ugly Servo Motors Get a Makeover

Machinery is a beautiful thing, but we’ve seen some pretty ugly servo motors from our surplus buys and our customers’ machines when they send them for repair.

Case in point:

Our Process

The remanufacturing process can differ depending on who’s doing it. Here’s a look at ours: 
  1. Moisture? Run a Meg test to check if moisture grounded the motor. If moisture has compromised the stator, the motor is disassembled and the windings are washed and baked. Afterwards, the unit is Meg tested again.
  2. Check the servo motor’s components. The bearings, housing, and end bells are checked for wear and/or damage.
  3. Verify and machine as needed. We look at the bearing seats to ensure that they within correct tolerance. Also, we look over the shaft to verify straightness and the condition of the shaft extension. If anything is worn or out of spec, we machine it to proper specs.
  4. More component checking. We go over all connectors, encoder covers, release voltage, and independent torque testing of all brake assemblies.
  5. Test the motor’s feedback devices. We verify that each feedback device – encoder, resolver, hall sensor, and tachometer – to make sure they are counting and functioning properly. If they’re bad, we either repair or replace the parts.
  6. More tests. We conduct a Back EMF test to check the magnetic strength of the rotor.
  7. Surge tests and winding. The stator receives a Surge Test and then a complete electrical winding evaluation to verify the quality of the winding.  If the stator fails we rewind it, in-house. The servo stator is then dipped in epoxy resin and baked to set the finish on the windings.
  8. Replace the bearings. All bearings are replaced with high grade shielded bearings for long life and performance.
  9. Replace seals and connectors. We replace all seals, O-rings, connectors, and any necessary worn or damaged parts.
  10. Reassemble. The servo motor is reassembled and aligned back to manufacture specs.
  11. Manufacturer-specific run testing. After all necessary steps are completed, the motor is run-tested with a manufacturer’s drive and complete servo system to simulate a real machine. Data is gathered and analyzed (e.g. amp, voltage, RPM). Load testing is performed to match the manufacturer’s torque/speed curve at a minimum of 3 different run speeds.
  12. Make it look pretty! The final step in our remanufacture process is to buff and paint the motor and create new nameplates when needed. Once this is complete, the servo motor has a like-new appearance.
A used servo motor can be a great alternative to buying a brand new one, but that really depends on who is supplying it. If you find your model number in stock from a surplus carrier, check to make sure that their remanufacturing process is up to standard. Warranties are common for those companies who stand behind their work. Choose a quality used and remanufactured servo motor once and prevent future breakdowns. As Repair Zone Man says, "No downtime!"

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